Earth-boring tools for forming boreholes in subterranean earth formations such as for hydrocarbon production, carbon dioxide sequestration, etc., generally include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) include cutting elements fixed to a bit body of the drill bit. Similarly, roller cone earth-boring rotary drill bits may include cones that are mounted on bearing pins extending from legs of a bit body such that each cone is capable of rotating about the bearing pin on which it is mounted. A plurality of cutting elements may be mounted to each cone of the drill bit.
Drill bits having superabrasive drilling surfaces may provide improved performance in such down-hole environments. In particular, polycrystalline diamond compacts (PDCs) formed of small (e.g., micron-sized) diamond grains fused and bonded together in a high temperature, high pressure process (known in the art as an HTHP process) using a metal catalyst, and supported on a substrate (e.g., a cobalt-cemented tungsten carbide substrate), can be incorporated onto a drill bit. Such drill bits have been found to provide a superabrasive surface capable of cutting through hard rock for extended periods of time, and under severe down-hole conditions of temperature, pressure, and corrosive environments, while maintaining the integrity and performance of the drill bit.
PDC cutting elements in which the catalyst material remains in the diamond table are generally thermally stable up to a temperature of about 750° C., although internal stress within the cutting element may begin to develop at temperatures exceeding about 400° C. due to phase changes in the metal catalyst (e.g., cobalt, which undergoes a transition from the beta phase to the alpha phase) and/or differences in the thermal expansion of the diamond grains and the catalyst metal at the grain boundaries. Hence, over time, PDC drill bits are subject to cumulative failure modes. In the course of drilling, cutting elements can wear, fracture, or accumulate damage that can alter, limit, or significantly degrade their performance in the application to which they were applied. Degradation of cutter performance can cause delays in the drilling process, increasing the overall cost of producing a well.